java boolean operators on enums

Question

In my c++ code i do stuff like this a lot

enum BarType {
    BT_UNKNOWN              = 0,
    BT_NORMAL               = 1,
    BT_BAR_REST             = 2,
    BT_REPEAT_PREV_MEASURES = 3,
    BT_TYPE_MASK            = 0x03,

    ... etc
};
BarType GetBarType(int bn)  { return (BarType)(m_barType[bn] & BT_TYPE_MASK); }

Is there a way to do this in java other than making everything ints which I hate because I like the type checking I get with enums?

Thanks

Java do have enum. Read this: http://docs.oracle.com/javase/tutorial/java/javaOO/enum.html — Konfle Dolex, Feb 15 '13 at 08:23
BTW, the first piece of code in this link is probably what you want: http://stackoverflow.com/a/4531172/1488595 — Konfle Dolex, Feb 15 '13 at 08:25

score 3 · Answer 1 · answered Feb 15 '13 at 08:25

3

The cleanest solution would be to use a java.util.EnumSet for each mask. You can then test whether a given enum value is in the set corresponding to a mask.

answered Feb 15 '13 at 08:25

Patricia Shanahan

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thanks but that looks complex and slow and i do millions of these bit operations so i guess i'll have to stick with int – steveh Feb 15 '13 at 10:46
1

@steveh I don't think "looks complex and slow" is any substitute for measurement. As the documentation I linked to says: 'Enum sets are represented internally as bit vectors. This representation is extremely compact and efficient. The space and time performance of this class should be good enough to allow its use as a high-quality, typesafe alternative to traditional int-based "bit flags.' – Patricia Shanahan Feb 15 '13 at 17:29

Stephan · Answer 2 · 2013-02-15T11:57:03.753

1

You can use the values array on the enum probably to achieve something like that.

 public enum BarType { BT_UNKNOWN, BT_NORMAL, BT_BAR_REST, BT_REPEAT }
 private static final int BT_TYPE_MASK = 0x03;

 public BarType getBarType(int bn) {
      return BarType.values()[bn & BT_TYPE_MASK]; 
 }

The order in values is the order in which the enum items are defined.

edited Feb 15 '13 at 11:57

answered Feb 15 '13 at 08:25

Stephan

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what is bn in your example? if its type BarType then the & doesn't work – steveh Feb 15 '13 at 10:44
It was according to your example supposed to be an int. Edited it to clarify (and fix a typo). – Stephan Feb 15 '13 at 11:55

java boolean operators on enums

2 Answers2